I should have said Sport routes, but what the hell...
As Whispering (soon to be dad) Nic said, E2 and E5 give the best Trad routes, but I stand firm that 7c is the UK's best Sport grade. Having done Dominatrix recently, I've got to say it's (probably) the best single pitch I've done. And it's 7c. (BTW the other best route is The Ashes, which back up Bonjoy's idea that 7c+ is the grade...). Cm'on, New Dawn, what else is there...
